A linear saw blade is a cutting tool frequently used in a current hand saw and electric saw. After being mounted on the hand saw or the electric saw, the saw blade is subjected to an opposite-direction backward force from a workpiece in a forward direction and saw teeth are subjected to upward and downward opposite-direction forces during an upward and downward movement of the saw blade. As a result, the saw blade often deforms during machining, where the saw blade may deform in a linear direction or deform in a direction vertical to the linear direction. In addition, because the saw blade has elasticity, some error is produced when the saw blade is mounted.
Due to many factors such as deformation of the saw blade under a stress, an error of a machine tool, and properties of the workpiece, the linear saw usually produces a machining error during each time of cutting and machining, and a value of the machining error varies each time. The errors accumulate till the saw blade deforms to the highest degree. Because the saw tooth or saw teeth contact the workpiece all the time in a machining process of the current saw blade, deformation produced during previous machining cannot be eliminated, and retain and accumulate all the time, to form an accumulated error, which affects machining precision and further shortens service life of the saw blade.
The aforementioned technical problems of the traditional linear saw are specifically described below by using an example of forming a straight gap on a wooden board.
During an upward and downward movement of the linear saw, stress (a force acting by a workpiece on saw teeth) in a vertical direction (a Z-axis direction) is exerted, and this direction does not coincide with a central line of the linear saw, thereby generating torque. Moreover, a saw blade used for forming a gap is generally thin, and its rigidity is insufficient in a direction vertical to a plane in which the saw tooth or saw teeth and a saw back locate. Therefore, the saw blade bends, and two sides of the saw blade usually bend, that is, a bend usually appears in a Y-axis direction, as shown in FIG. 1.
In addition, during machining, the saw blade is usually subjected to unbalanced stress on the left and right sides under the influence of many factors such as heterogeneous materials of the machined wooden board. The saw blade also bends during machining when being subjected to uneven stress. The saw blade may deviate from a machining position and a machining direction due to the bend, so that a position of the saw blade and a position of the to-be-machined straight gap are not on the same line. An X-axis direction of the saw blade cannot keep parallel with the to-be-machined straight line and a deviation angle is formed therebetween, as shown in FIG. 2a and FIG. 2b. In the figures, a black segment indicates the linear saw, FIG. 2a shows a straight-line machining effect (also can be regarded as an ideal straight-line machining effect) at an initial state, and FIG. 2b shows a straight-line machining effect in which a deviation angle is formed.
After the deformation of the saw blade results in deviation in a machining path, due to certain height of the saw tooth or saw teeth and certain thickness of the machined wooden board, the saw tooth or saw teeth are clamped in the gap which is previously formed by cutting and deviates at a certain angle, so that the saw blade continuously advances and operates at the deviation angle as before. In this way, the saw blade deviates farther and farther, which leads to an accumulated deviation, or in other words, an accumulated machining error. FIG. 2b additionally shows a certain accumulated deviation. Further, in order to ensure a straight-line machining position, the two ends of the linear saw usually stay in the Z-axis direction. As a result, as a machining path deviates at a bigger angle, the linear saw deforms to a higher degree. That is to say, during accumulation of the machining errors, deformation errors of the linear saw also accumulate.
In addition, the deformation of the saw blade further leads to an opposite-direction restoring force which can straighten the saw blade. Because the aforementioned deformation accumulates and worsens, when the restoring force produced due to the deformation of the saw blade is greater than a deviation clamping force produced due to gap deviation, the saw blade begins to restore towards a direction opposite to the deviation, and a machining path deviates towards a direction opposite to a deviation direction shown in FIG. 2b, till the saw blade returns to a straight-line machining position (FIG. 2c). Then, the saw blade continuously operates in a direction (probably opposite to or identical with the direction in FIG. 2b) to produce machining error accumulation and deformation accumulation (FIG. 2d), till returns to the straight-line machining position again (FIG. 2e).
Such a process in which the saw blade deviates towards one direction, returns to the straight-line machining position, deviates again, and then returns to the straight-line machining position again repeatedly occurs, so that the formed line is not straight and a machining path changes all the time, and typically, an S-shaped machining path is formed. Moreover, if the produced deviation clamping force is so high that the saw blade deforms to an unbearable degree, and the saw blade is probably broken. In an existing solution, to decrease the accumulated error and make improvement, only the following paths can be used: strengthen the rigidity of the saw blade, decrease an error of the machine tool, and optimize the properties of the workpiece. However, the error cannot be eliminated fundamentally, thereby leading to low machining position precision of the existing linear saw.